Liquefied gas production facilities are facilities for producing liquefied natural gas by refining and liquefying liquefied natural gas (LNG), liquefied petroleum gas (LPG), and synthetic natural gas (SNG), which are natural gases. Examples of liquefied gas production facilities include an LNG production facility, an LPG production facility, and an SNG production facility.
FIG. 1 is a functional block diagram illustrating an example of an LNG production facility. Gas supplied from a gas field is fed to the LNG production facility after a liquid separation process. In the LNG production facility, LNG is produced by the steps of, for example, removal of mercury from the gas, acid gas removal, moisture removal, liquefaction, and nitrogen removal.
A refrigerant used in the liquefaction step is circulated by a vapor compression refrigeration cycle. In the refrigeration cycle, a gas refrigerant is compressed by a compressor, and the compressed refrigerant is cooled by a condenser, so that the refrigerant is liquefied. Then, the pressure and temperature of the refrigerant are reduced by an expansion valve or the like, and the refrigerant is caused to exchange heat with natural gas, so that the gas refrigerant is generated again. Thus, the natural gas is liquefied by the refrigeration cycle that utilizes power of the compressor and heat exchange in the condenser.
Refrigeration cycles of LNG production facilities include water-cooling or air-cooling condensers. Water-cooling condensers often use seawater to cool cooling water. However, the influence of the seawater heated as a result of heat exchange raises environmental concerns, and the number of LNG production facilities including air-cooling condensers has recently increased.
The liquefaction step is essential not only in LNG production facilities but also in LPG production facilities and SNG production facilities.
As illustrated in FIGS. 1 and 2 of PTL 1, an LNG production facility is generally configured such that a pipe rack is arranged in a central area of the facility and that compressors, heat exchangers for cooling natural gas, a distillation column for refining the natural gas, etc., are arranged on both sides of the pipe rack. In an LNG production facility including an air-cooling condenser, a plurality of air fin coolers (referred to also as “AFCs”) are arranged at the top of the pipe rack.
In the LNG production facility, the air fin coolers are arranged at least along a single straight line so as to form a rectangular shape as a whole. The LNG production facility has a rectangular shape as a whole since facilities related thereto are arranged on both sides of the pipe rack having the air fin coolers at the top.
In recent years, the size of LNG production facilities has been increased. Accordingly, one or two LNG production facilities are generally constructed at the initial stage of a project, and another LNG production facility (facilities) is additionally constructed in accordance with the increase in demand. The LNG production facilities that are constructed as necessary in accordance with the progress of the project are formed as modules of substantially the same type, and are referred to as, for example, “LNG trains”, “LNG modules”, or “LNG units”.
In FIG. 1 of PTL 2, a plurality of LNG modules 20 are arranged next to each other.